Wireless Power Transfer Device

ABSTRACT

There is provided a wireless power transfer device comprising an input interface configured to receive a primary magnetic flux in a first direction, an output interface configured to output a secondary magnetic flux in a second direction different from the first direction, wherein the input interface and the output interface form a closed electric circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application of InternationalApplication No. PCT/FI2011/050402, filed May 3, 2011, which claimsbenefit to Finnish Application No. 20105493, filed May 7, 2010, whichare incorporated by reference herein in their entirety.

BACKGROUND

1. Field

The invention relates generally to wireless power transfer. Moreparticularly, the invention relates to redirecting a magnetic flux by awireless power transfer device.

2. Description of the Related Art

It is known to charge a certain type of devices, such as toothbrushes,wirelessly over a magnetic connection. That is, by using a magnetic fluxoriginating from a charger and penetrating into the device beingcharged, for example.

However, this type of charging involves several problems. These relate,for example, to the physical limitations of the devices, orientation ofthe devices, and efficiency of the charging process.

SUMMARY

Embodiments of the invention seek to improve the applicability ofwireless charging.

According to an aspect of the invention, there are provided apparatusesas specified in claims 1 and 8.

According to an aspect of the invention, there is provided a system asspecified in claim 13.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail withreference to the embodiments and the accompanying drawings, in which

FIGS. 1A, 1B and 10 present a wireless power transfer device accordingto an embodiment;

FIGS. 2A and 2B show a wireless power transfer device according to someembodiments;

FIG. 3 shows an external device being charged according to anembodiment;

FIG. 4 illustrates a support structure of the wireless power transferdevice according to an embodiment;

FIG. 5 illustrates a casing of the wireless power transfer deviceaccording to an embodiment;

FIG. 6 presents a wrist device adapted around the casing of the wirelesspower transfer device according to an embodiment;

FIG. 7 presents a wireless power transfer device according to anembodiment;

FIG. 8 illustrates a wrist device according to an embodiment; and

FIGS. 9A and 9B illustrate rotation of a display.

DETAILED DESCRIPTION

The following embodiments are exemplary. Although the specification mayrefer to “an”, “one”, or “some” embodiment(s) in several locations ofthe text, this does not necessarily mean that each reference is made tothe same embodiment(s), or that a particular feature only applies to asingle embodiment.

According to electromagnetic induction theory, an alternating externalmagnetic flux induces a voltage to a conductor, such as to a coil. Thevoltage induced to the coil is given by e=−NAdB/dt, where B is thedensity of the magnetic field, A is the surface area of the coil, and Nis the number of loops in the coil. The minus sign denotes that thepolarity of the induced voltage e is such that it drives such anelectric current to the coil that a magnetic field generated by theelectric current opposes the change in the magnetic flux which producedthe voltage e. Therefore, the induced electric current may generateanother magnetic field that is oriented in the direction of the normalof the coil surface.

The induction phenomenon may be used in wireless charging of an externaldevice, for example, by directing a magnetic flux of the magnetic fieldto the external target device being charged. Accordingly, genericinductive-based recharging devices are available, which can be used forrecharging electric devices. Typically in inductive charging, themagnetic flux is generated by supplying electric current to a coil. Thealternating electric current in the coil generates the magnetic fieldcausing the magnetic flux. The reception of the magnetic flux enables anelectric current to be generated to a coil of the external device.

One of the requirements for a successful charging is that the providerof the magnetic flux and the external device are inductively connectedto each other. That is to say that the magnetic flux at least partlypenetrates the coil of the external device. Optimal charging takes placewhen the direction of the magnetic flux is parallel with the normal ofthe coil plane of the external device, and the magnetic flux goesthrough the coil. This is because then the magnetic flux takes aquantity of BA, where B is the density of the magnetic field and A isthe surface area of the coil. As a consequence, devices to be used forsuch recharging typically have a planar shape, and they can be placed ona table, for example. This often enables the magnetic coil of thecharger and the external target device to be co-planar and to be placedon top of each other in a repeatable manner. Such devices are mobilephones, music players, and game controllers, for example. Moreparticularly, such devices have a shape which encourages the user toplace the device onto the charger in the most suitable position in termsof the charging efficiency.

However, it often occurs that the coil of the device to be chargeddeviates from the co-planar orientation with the coil of the charger, inwhich case the quantity of the magnetic flux is proportional to cos(α),where a denotes the angle of the magnetic flux with respect to thenormal of the surface of the coil. This leads to non-optimal or evenimpossible charging of the external device. This is especially the casewith wrist devices because their structure is not beneficial to suchwireless recharging.

A wrist device is a device which typically comprises a wrist band whichcan be attached to the user's wrist.

In an embodiment of the invention, the wrist device is a watch.

In an embodiment, the wrist device is a performance monitor capable ofrecording a performance data which characterize user's performance. Suchperformance data comprise cardiovascular data, such as heart rate, heartbeat intervals, electrocardiographic data or heart rate variation data.In an embodiment, the performance data comprises motion data, such asacceleration data, speed data or location data, characterizing user'smotion or instantaneous location.

In an embodiment of the invention, the wrist device is a wrist mobilephone.

Wrist devices seldom have planar structures which would enable a properrecharging position. The usual planar structures in wrist devices are aglass or a plastic shield in front of a display, and a back plate. Wristdevices are often treated as watches, which are considered to be fragileand prone to scratches. Therefore, users are hesitant to place the wristdevice face (such as the display) down on a recharging device. On theother hand, a wrist strap often prevents the wrist device from beingpositioned face up on the charger. Therefore, the wrist devices may beput on the charger sidewise such that a side of the wrist watchincluding the wrist straps lies against the charger. However, astraightforward place for positioning the coil in the wrist watch isbetween the display and the back plate. This causes non-optimal chargingdue to the orientation of the magnetic flux with respect to the coil ofthe wrist device. In the worst case, the coil of the wrist device isperpendicular to the coil of the charger.

As a solution, a wireless power transfer device 100 is provided as shownin FIGS. 1A, 1B and 1C according to an embodiment. FIG. 1A shows a topview of the device 100, FIG. 1B presents a side view of the device 100,and FIG. 10 is a diagonal view of the device 100. The wireless powertransfer device 100 may comprise an input interface 102 for receiving aprimary magnetic flux 104 in a first direction. The wireless powertransfer device 100 may further comprise an output interface 106configured to output a secondary magnetic flux 108 in a second directiondifferent from the first direction. According to an embodiment, theinput interface 102 and the output interface 106 form a closed electriccircuit. Accordingly, the wireless power transfer device 100 may be apassive device. In other words, the input interface 102 and the outputinterface 106 are connected together via galvanic links 110A and 110B.The links 110A and 110B may be wires conducting an electric currentbetween the input interface 102 and the output interface 106. As shown,the secondary magnetic flux 108 is directed to the normal of the surfaceof the output interface 106 providing the secondary magnetic flux 108.

In an embodiment, the first and the second directions are perpendicularto each other, as FIGS. 1A, 1B and 1C show. This means that the planesof the input interface 102 and the output interface 106 areperpendicular to each other. However, the first and the seconddirections may not be perpendicular to each other. FIGS. 2A and 2B showtwo cases where the directions of the magnetic fluxes 104/108 aredifferent from each other but not perpendicular. FIGS. 2A and 2B showangles 112 and 114, respectively, between the planes of the input 102and the output 106 interfaces. Accordingly, the angle may be smallerthan 90 degrees, as is the case in FIG. 2A, or larger than 90 degrees,as is the case in FIG. 2B. Redirecting the direction of the magneticflux enables a variety of different physical structures to be placed inconnection with the wireless power transfer device 100.

FIG. 3 shows a possible use of the secondary magnetic flux 108 accordingto an embodiment. In FIG. 3, the output interface 106 charges anexternal device 300 with the secondary magnetic flux 108. The externaldevice 300 may comprise an interface 302 such as a magnetic coil forreceiving the magnetic flux 108. The magnetic flux 108 may induce anelectric current to the coil 302 which electric current is used tocharge a battery 304 of the external device 300.

According to an embodiment, the wireless power transfer device 100further comprises a supporting structure 420 for supporting the wirelesspower transfer device 100 with respect to an external device 400providing the primary magnetic flux 104. The supporting structure 420may be integrated into a casing of the wireless power transfer device100, in which case the supporting structure 420 may form the bottom sideof the casing. The supporting structure 420 may be placed on the top ofthe external device 400 comprising a coil 402. The external device 400may be of a planar shape so that the coil 402 is placed in the sameplane inside the external device 400. The external device 400 providingthe magnetic flux 104 may be a flat structure, such as a mat or thelike, comprising the coil and a power intake, possibly a wired powerintake. The power taken in causes an electric current to flow in thecoil 402, which causes the magnetic flux 104 to emerge.

Alternatively, no external device 400 providing the magnetic flux 104 isnecessary when the wireless power transfer device 100 includes a powerintake in a form of a wire. The power can then be used in generating theelectric current in the output interface 106. Hence, in this case noneed for the input interface 102 is necessary.

According to an embodiment, the input interface 102 comprises a primarycoil, and the output interface 106 comprises a secondary coil, whereinthe primary coil is oriented with respect to the supporting structure420 so as to receive the primary magnetic flux 104. By applying anappropriate supporting structure with respect to the plane of the coil402 of the external device 400, efficient charging may be obtained dueto the beneficial orientation of the magnetic flux 104 with respect tothe primary coil. Gravitation may keep the wireless power device 100against the external device 400. Alternatively, attachment means, suchas clips, may be provided for attaching the supporting structure 420 (orthe casing) to the external device 400.

The primary and secondary coils may have a ferrite core or an air core.The coils may be implemented with wires or based on printed boards. Theprimary and secondary coils of the wireless power transfer device 100may be of different sizes, or their surface area may be the same. Thenumber of loops in each coil may vary as well. The coil material iselectrically conductive material, such as copper or aluminum.

In addition to the direction of the magnetic flux with respect to thereceiving coil, the recharging efficiency is proportional to the area Aof the coil. In practice this means that the coil in the target deviceto be charged is beneficially positioned in a dimension which allowslarge coil areas. According to an embodiment, the primary loop of thewireless power transfer device 100 has a large surface area A₁ so thatit can efficiently receive the energy carried in the primary magneticflux 104. The received energy can then be transferred to the externaldevice 300 to be charged via the secondary coil. This enables efficientgathering of the energy with the large coil surface area A₁ and theoutput of the energy to the external device 300 with the secondary coilthat may be designed to match the coil of the external device 300 beingcharged.

In an embodiment of the invention, the inductance of the input interface102 matches the inductance of the external device 400. A matching may beimplemented by choosing the area of a primary coil and/or the number ofloops so that appropriate mutual inductance between the primary coil andthe recharging circuitry of the external device 400 is obtained.

In an embodiment of the invention, the inductance of the outputinterface 106 matches the inductance of the recharging circuit of thewrist device. A matching may be implemented by choosing the area of asecondary coil and/or the number of loops so that appropriate mutualinductance is obtained between the secondary coil and the rechargingcircuitry of the wrist device.

According to an embodiment, the wireless power transfer device 100 mayfurther comprise a casing 520 supporting the input interface 102 and theoutput interface 106 as shown in FIGS. 5 and 6. The casing 520 may havea variety of physical structures. It also functions as a shield for theinterfaces 102 and 106. Furthermore, the casing 520 functions as acontact surface for or a receiver of the external device 300 of FIG. 3.Accordingly, the physical structure of the casing 520 may be selectedaccording to the physical structure of the external device 300 to beassociated with the wireless power transfer device 100. In oneembodiment, the casing 520 is a rectangular box. The material for thecasing may be plastic, for example.

According to an embodiment, the casing 520 receives a wrist device 600and the output interface 106 is directed with respect to the casing 520so as to direct the secondary magnetic flux 108 to a target area of thewrist device 600, as shown in FIG. 6 which is a top view. The targetarea of the wrist device may be the area where the coil 602 of the wristdevice 600 is located. To further aid the reception of the wrist device600 on the casing 520, the casing 520 may comprise a receiving surface522 for receiving the backside of the wrist device 600. The receivingsurface may be a vertical flat surface, for example, so that the wristdevice 100 may be put on the wireless power transfer device 100sidewise. By sidewise it is meant that one side of the wrist device 600along with the wrist straps 604A and 604B rests on the casing, as shownin FIG. 6.

According to an embodiment, the casing 520 further comprises supportmembers 524A and 524B for supporting the wrist straps 604A and 604B ofthe wrist device 600. The wrist straps 604A and 604B may be put betweena main body 521 of the casing 520 and the support members 524A and 524B.The support members 524A and 524B may be vertically extending elementspreventing the wrist straps 604A and 604B, respectively, from movingsignificantly with respect to the wireless power transfer device 100.Similarly, the main body 521 of the casing 520 may be a verticallyextending element allowing the wrist straps 604A and 604B to surroundthe main body 521 of the casing 520. Therefore, the main body 521 of thecasing 520 may have an at least partly circular shape, although it mayalso have the flat surface 522 for receiving the back plate of the wristdevice 600.

In an embodiment, the coil of the wrist device 600 is integrated intothe wrist straps 604A and 604B in which case no wireless power transferdevice 100 is needed. When the wrist device 600 is placed sidewise, thecoil of the wrist device 600 is co-planar with the planar-shapedexternal device 400 providing the primary magnetic flux 104. This waythe magnetic flux is efficiently captured by the coil in the wriststraps 604A and 604B.

According to an embodiment, instead of being a passive device comprisingthe coil circuitry of the primary and the secondary coils connectedtogether to form the closed electric circuit, the wireless powertransfer device 100 may further comprise a circuitry 700 fortransferring data over the output interface 108. That is to say that thewireless power transfer device 100 may communicate with the externaldevice 300/600 receiving the secondary magnetic flux 108. This enablesthe wireless power transfer device 100 to transmit data to the externaldevice 300/600, or the wireless power transfer device 100 to receivedata from the external device 300/600. The data may include instructionsbeing given to the external device 300/600 regarding the operation ofthe external device 300/600.

According to an embodiment, the wireless power transfer device 100 mayfurther comprise a communication interface 702 for accessing a network704 in order to communicate data with the network 704. The transfer ofdata to the network 704 over the communication interface 702 may takeplace wirelessly or via a wire. The communication interface 702 mayoperate under a Wireless Local Area Network (WLAN), a BlueTooth, aBlueTooth Low Energy, a ZigBee, or an ANT, for example, forcommunicating with a wireless network or a computer. In order totransmit the data to the network 704 wirelessly, the wireless powertransfer device 100 may comprise at least one antenna.

This is beneficial so that if there is data stored in the externaldevice 300/600 that needs to be transferred to the network 704, the datamay be first transferred to the wireless power transfer device 100 overthe magnetic fields and then over the communication interface 702 to thenetwork 704. This way, the external device 300/600 may perform the datatransfer while the external device 300/600 is being charged so that theuser may not need to transfer the data separately via the computer, forexample.

An exemplary case where data may need to be transferred is when theexternal device 300/600 is a performance monitor or a personal exercisecomputer, for example, and the performance monitor has exerciseinformation stored in its memory. Typically, a user would transfer theexercise data to a separate computer and analyze the exercise by usingthe separate computer. According to the embodiment, the user need not dothis transfer separately, because the wireless power transfer device 100performs the transfer automatically while the performance monitor isbeing recharged. One exemplary scenario is that the user puts theperformance monitor on charge for the night time and the data stored inthe performance monitor is transferred via the output interface 106 andthe communication interface 702 to the network 704 which the separatecomputer is either connected to or connectable to.

The data transfer embodiment allows for a higher power consumption ofthe external device 300/600 when transferring data, because the datatransfer takes place when the external device 300/600 is being chargedby the wireless power transfer device 100. The embodiment further allowsfor freedom in the implementation of the external device 300/600,because no need may exist to implement any wireless communicationinterface operating under WLAN, for example. This allows for a thinnerphysical structure of the external device 300/600.

The circuitry 700 and the communication interface 704 may be powered bythe coil circuitry comprising the primary and the secondary coilsconnected together as the closed electric circuit, as shown in FIG. 7.

The wireless power transfer device 100 may further comprise a memoryconnected to the circuitry 700. However, memory may also be integratedin to the circuitry 700 and, thus, no separate memory may be required.The memory may store the data to be communicated with or received fromthe external device 300/600 and/or the network 704.

There is also provided a wrist device 800. A very general architectureof the wrist device according to an embodiment is shown in FIG. 8. FIG.8 shows only the elements and functional entities required forunderstanding the wrist device 800 according to an embodiment. Othercomponents have been omitted for reasons of simplicity. Theimplementation of the elements and functional entities may vary fromthat shown in FIG. 8. The connections shown in FIG. 8 are logicalconnections, and the actual physical connections may be different. Theconnections can be direct or indirect and there can merely be afunctional relationship between components. It is apparent to a personskilled in the art that the wrist device 800 may also comprise otherfunctions and structures.

The wrist device may be associated with the wireless power transferdevice 100 so that a coil 802 of the wrist device 800 may receive thesecondary magnetic flux 108 from the output interface of the wirelesspower transfer device 100. In order to receive the magnetic fluxefficiently, the wireless power transfer device 100 may comprise thecasing 520 for receiving the wrist device 800 so that the wrist device800 may be put optimally with respect to the secondary coil (acting asthe output interface 106) of the wireless power transfer device 100.Then the coil 802 and the secondary coil of the wireless power transferdevice 100 may be co-planar or at least close to co-planar.

The wrist device 800 may further comprise a user interface 810. The userinterface may comprise a display for showing information, an acousticspeaker for producing sounds, touch sensors for sensing a touch of auser, a motion sensor for sensing the motion of the wrist device 800,for example.

The wrist device 800 may further comprise a detection circuitry 804 fordetecting the presence of the secondary magnetic flux 108. The detectionof the secondary magnetic flux 108 may take place such that thedetection circuitry 804 detects an emerging current in the coil 802 or abattery 806 being charged, for example.

The wrist device 800 may further comprise a user interface controller808 for setting the user interface into a recharging mode when thesecondary magnetic flux 108 has been detected. In other words, the wristdevice 800 has certain functionalities while the wrist device 800 isbeing recharged by the power transfer device 100. These functionalitiesmay be different from the functionalities of a normal, non-recharging,mode. In order to obtain knowledge regarding the detection of thesecondary magnetic flux, the detection circuitry 804 is connected to theuser interface controller 808. The use of a different operation mode ofthe wrist device 800 when connected to the wireless power transferdevice 100 is beneficial so that the wrist device may automaticallyperform certain actions without any user input. The wrist device 800 maycomprise a memory connected to the controller 808. However, memory mayalso be integrated to the controller 808 and, thus, no separate memorymay be required. The memory may be used to store information ordifferent configurations related to the recharging mode, for example.The functionalities of the recharging mode may be preconfigured in thewrist device 800.

When the user interface comprises a display 810, the recharging mode mayinclude at least one of the following processes: illuminating thedisplay and rotating the view on the display. The user interfacecontroller 808 may perform the illumination of the display by switchingthe illumination of the display on. The light may be provided byseparate light sources, such as light emitting diodes (LEDs). There mayalso be an optical fiber guiding the light to the display. Theillumination is beneficial when a user wishes to use the wrist device800 as a night watch. Then the user may put the wrist device 800 on thecasing of the wireless power transfer device 100. The user interfacecontroller 808 may, after being notified by the detection circuitry 804,turn on the recharging mode according to which the display is lit.

The rotation of the view of the display may be such that the view isrotated 90 degrees. This is beneficial so that the user looking at thedevice 800 from a viewing direction 812 need not to turn his/her headwhen reading the information on the display. Instead the information,such as time, date and/or a picture, on the display is rotated to anupright position so that the view is readable when the wrist unit istilted. Imagine that a user sets the wrist watch 800 on the wirelesspower transfer device 100 as shown in FIG. 6. Then the orientation ofthe information on the display is not upright but horizontal. As aconsequence, the user is not able to read the information on the displayas easily as he/she desires. Rotating the view 90 degrees when the userinterface controller 808 is notified by the detection circuitry 804changes the orientation of the information to an upright (vertical)orientation so that the information being displayed may be easily readby the user.

The rotation of the display is shown in FIGS. 9A and 9B. FIG. 9A showsthe wrist device 800 equipped with the wrist straps 604A and 604B, oneor more buttons 814A and 814B, and a display 900 for showing information902. The information 902 may be text strings, numeric values orpictures, for example. Same elements are shown in FIG. 9B. However, inFIG. 9A the wrist device 800 is not in the recharging mode and thereforethe information 902 shown in the display 900 is not upright. This makesthe information difficult to read when the wrist device 800 is placedtilted on a table, for instance. In FIG. 9B, the wrist device is in therecharging mode, which causes the information 902 in the display 900 tobe rotated 90 degrees so that the information 902 in the display 900 iseasily read when the wrist device 800 is tilted.

The user interface 810 may comprise an input interface 814, such as atleast one button 814A and 814B. The user interface controller 808switches on the recharging mode when the user interface controller 808is notified of the presence of the magnetic flux 108. According to anembodiment, the recharging mode includes a process of reconfiguring theinput interface 814. The process of reconfiguring the input interface814 may include reconfiguring the functions performed by the at leastone button 814A and 814B. For example, when the wrist device 800 isplaced sidewise as shown in FIG. 6, the buttons pointing upwards mayhave a certain functionality different from the normal functionality.They may be configured to stop an alarm sound, activate an alarm clockfunctionality, or to initiate or cancel data transfer, for example. Whenno presence of the secondary magnetic flux 108 is detected anylonger,the configuration of the input interface 814 is restored to its normal,original state, for example. The input interface 814 may also comprisemicrophones for receiving acoustic instructions. These may also bereconfigured such that when the user gives an order “stop”, the alarmclock goes silent, for example.

According to an embodiment, the wrist device 800 further comprises acommunication interface 816 for communicating data with a network 818.The detection circuitry 804 may initiate the process of communicatingdata automatically over the communication interface 816 to the network818. This is beneficial so that the data being stored in the wristdevice 800 may be trans-mitted automatically to the network 818 andpossibly to a computer connected to the network 818 without specificorders from the user. The user only needs to place the wrist watch 800on the wireless power transfer device 100. Thus, at the same time as thewrist watch 800 is being charged, it can transmit data to the network800. Alternatively, the communication interface 816 may receive datafrom the network 818. The data may be related to a software update ofthe wrist device 800, for example. The communication interface mayoperate under WLAN, BlueTooth, BlueTooth Low Energy, or proprietary datatransfer protocol or wireless data transfer technique. In order totransmit the data to the network 818 wirelessly, the wrist device 800may comprise at least one antenna.

According to an embodiment, the wrist device 800 may further comprise aninterface 820 for exchanging data with the wireless power transferdevice 100 over the coil 802 and the output interface 108 of thewireless power transfer device 100. The detection circuitry 804 mayinitiate the data transfer over the interface 820 when the secondarymagnetic flux 108 has been detected. This is advantageous so that thedata being stored in the wrist device 800 may be transmitedautomatically to the wireless power transfer device 100 and possiblyfurther to the network 704 as shown in FIG. 7.

As used in this application, the term ‘circuitry’ refers to all of thefollowing: (a) hardware-only circuit implementations, such asimplementations in only an analog and/or digital circuitry, and (b)combinations of circuits and software (and/or firmware), such as (asapplicable): (i) a combination of processor(s) or (ii) portions ofprocessor(s)/software including digital signal processor(s), software,and memory(ies) that work together to cause an apparatus to performvarious functions, and (c) circuits, such as a microprocessor(s) or aportion of a microprocessor(s), that require software or firmware foroperation, even if the software or firmware is not physically present.

This definition of ‘circuitry’ applies to all uses of this term in thisapplication. As a further example, as used in this application, the term‘circuitry’ would also cover an implementation of merely a processor (ormultiple processors) or a portion of a processor and its (or their)accompanying software and/or firmware. The term ‘circuitry’ would alsocover, for example and if applicable to the particular element, abaseband integrated circuit or applications processor integrated circuitfor a mobile phone or a similar integrated circuit in a server, acellular network device, or another network device.

The techniques and methods described herein may be implemented byvarious means. For example, these techniques may be implemented inhardware (one or more devices), firmware (one or more devices), software(one or more modules), or combinations thereof. For a hardwareimplementation, the devices 100 and/or 800 may be implemented within oneor more application-specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,other electronic units designed to perform the functions describedherein, or a combination thereof. For firmware or software, theimplementation can be carried out through modules of at least one chipset (e.g. procedures, functions, and so on) that perform the functionsdescribed herein. The software codes may be stored in a memory unit andexecuted by processors. The memory unit may be implemented within theprocessor or externally to the processor. In the latter case, it can becommunicatively coupled to the processor via various means, as is knownin the art. Additionally, the components of the systems described hereinmay be rearranged and/or complemented by additional components in orderto facilitate the achievements of the various aspects, etc., describedwith regard thereto, and they are not limited to the preciseconfigurations set forth in the given figures, as will be appreciated byone skilled in the art.

Certain embodiments may be implemented as computer programs in the wristdevice 800 or in the wireless power transfer device 100 according to theembodiments. The computer programs comprise instructions for executing acomputer process. The computer program implemented in the wireless powertransfer device 100 may carry out, but is not limited to, the tasksrelated to FIG. 7. The computer program implemented in the wrist device800 may carry out, but is not limited to, the tasks related to FIG. 8.

The computer program may be stored on a computer program distributionmedium readable by a computer or a processor. The computer programmedium may be, for example but not limited to, an electric, magnetic,optical, infrared or semiconductor system, device or transmissionmedium. The computer program medium may include at least one of thefollowing media: a computer readable medium, a program storage medium, arecord medium, a computer readable memory, a random access memory, anerasable programmable read-only memory, a computer readable softwaredistribution package, a computer readable signal, a computer readabletelecommunications signal, computer readable printed matter, and acomputer readable compressed software package.

Even though the invention has been described above with reference to anexample according to the accompanying drawings, it is clear that theinvention is not restricted thereto but can be modified in several wayswithin the scope of the appended claims. Further, it is clear to aperson skilled in the art that the described embodiments may, but arenot required to, be combined with other embodiments in various ways.

1. A wireless power transfer device comprising: an input interfaceconfigured to receive a primary magnetic flux in a first direction; andan output interface configured to output a secondary magnetic flux in asecond direction different from the first direction, the input interfaceand the output interface forming a closed electric circuit.
 2. Thewireless power transfer device of claim 1, wherein the output interfaceis configured to charge an external device with the secondary magneticflux.
 3. The wireless power transfer device of claim 1, furthercomprising a supporting structure for supporting the wireless powertransfer device with respect to an external device providing the primarymagnetic flux, the input interface comprising a primary coil, the outputinterface comprising a secondary coil, the primary coil being orientedwith respect to the supporting structure so as to receive the primarymagnetic flux.
 4. The wireless power transfer device of claim 1, whereinthe wireless power transfer device further comprises a casing supportingthe input interface and the output interface, the casing beingconfigured to receive a wrist device, the output interface beingdirected with respect to the casing so as to direct the secondarymagnetic flux to a target area of the wrist device.
 5. The wirelesspower transfer device of claim 4, wherein the casing further comprises:a receiving surface for receiving a backside of the wrist device; andsupport members for supporting wrist straps of the wrist device.
 6. Thewireless power transfer device of claim 1, further comprising acircuitry configured to transfer data over the output interface.
 7. Thewireless power transfer device of claim 6, further comprising acommunication interface for accessing a network in order to communicatedata with the network.
 8. A wrist device, comprising: a user interface;a coil configured to receive a secondary magnetic flux from a wirelesspower transfer device; a detection circuitry for detecting the presenceof the secondary magnetic flux; and a user interface controller forsetting the user interface into a recharging mode when the secondarymagnetic flux has been detected.
 9. The wrist device of claim 8, whereinthe user interface comprises a display, the recharging mode comprisingat least one of the following processes: illuminating a display androtating a view on the display.
 10. The wrist device of claim 8, whereinthe user interface comprises an input interface, the recharging modecomprising a process of reconfiguring the input interface.
 11. The wristdevice of claim 8, wherein the wrist device further comprises acommunication interface configured to communicate data with a network,the detection circuitry being further configured to initiate datatransfer over the communication interface when the secondary magneticflux has been detected.
 12. The wrist device of claim 8, wherein thewrist device further comprises an interface configured to exchange datawith the wireless power transfer device over the coil and an outputinterface of the wireless power transfer device, the detection circuitrybeing further configured to initiate data transfer over the interfacewhen the secondary magnetic flux has been detected.
 13. A systemcomprising: a wireless power transfer device, the wireless powertransfer device comprising: an input interface configured to receive aprimary magnetic flux in a first direction; an output interfaceconfigured to output a secondary magnetic flux in a second directiondifferent from the first direction, the input interface and the outputinterface forming a closed electric circuit; and a wrist device, thewrist device comprising: a user interface; a coil configured to receivea secondary magnetic flux from the wireless power transfer device; adetection circuitry for detecting the presence of the secondary magneticflux; and a user interface controller for setting the user interfaceinto a recharging mode when the secondary magnetic flux has beendetected.
 14. The system of claim 13, wherein the wireless powertransfer device further comprises a supporting structure for supportingthe wireless power transfer device with respect to an external deviceproviding the primary magnetic flux, the input interface comprising aprimary coil, the output interface comprising a secondary coil, theprimary coil being oriented with respect to the supporting structure soas to receive the primary magnetic flux.
 15. The system of claim 13,wherein the wireless power transfer device further comprises a casingsupporting the input interface and the output interface, the casingbeing configured to receive the wrist device, the output interface beingdirected with respect to the casing so as to direct the secondarymagnetic flux to a target area of the wrist device.
 16. The system ofclaim 15, wherein the casing comprises: a receiving surface forreceiving a backside of the wrist device; and support members forsupporting wrist straps of the wrist device.
 17. The system of claim 13,wherein the wireless power transfer device further comprises a circuitryconfigured to transfer data over the output interface, and the wristdevice further comprise an interface configured to exchange data withthe wireless power transfer device over the coil and the outputinterface of the wireless power transfer device, the detection circuitrybeing further configured to initiate data transfer over the interfacewhen the secondary magnetic flux has been detected.
 18. The system ofclaim 17, wherein the wireless power transfer device further comprises acommunication interface for accessing a network in order to communicatethe data with the network.
 19. The system of claim 13, wherein the userinterface comprises a display, the recharging mode comprising at leastone of the following processes: illuminating a display and rotating aview on the display.
 20. The system of claim 13, wherein the userinterface comprises an input interface, the recharging mode comprising aprocess of reconfiguring the input interface.